Eco-friendly synthesis of electrochemiluminescent nitrogen-doped carbon quantum dots from diethylene triamine pentacetate and their application for protein detection

An eco-friendly approach for the synthesis of nitrogen-doped carbon quantum dots (NCQDs) has been developed by the carbonization of diethylene triamine pentacetate acid (DTPA). In contrast to previous methods, neither strong acid treatment nor further surface modification is necessary for this synthetic process. The prepared NCQDs with average diameters of 2.5 nm exhibit excitation-independent photoluminescent behavior. Furthermore, the synthetic NCQDs have abundant carboxy groups and exhibit strong electrochemiluminescent (ECL) activity with K2S2O8 as coreactant on the glassy carbon electrode (GCE). Compared to pure CQDs, NCQDs exhibited stronger and more stable ECL signals due to easier electro-reduction of NCQDs generating more abundant NCQDs−. Importantly, these NCQDs are demonstrated to be excellent ECL luminophor for protein detection due to their stable emission, well dispersibility, low toxicity and good compatibility with biomolecules. Accordingly, the NCQDs were used to construct a novel ECL immunosensor for detection of human IgG (HIgG) which revealed good stability, reproducibility and selectivity.